1. Field of the Invention
The present invention relates to power regulator, and more particularly, to an offline switching power regulator.
2. Description of Related Art
An offline power supply includes a power transformer to provide isolation from AC line input to the output of the power supply for safety. Various topologies are used for regulating the output of the power supply. Among them, the magnetic amplifier is a high efficiency solution. The circuit operation of magnetic amplifier is shown in a prior art of “Method and apparatus for magnetic amplifier to reduce minimum load requirement” by Yang, U.S. Pat. No. 6,501,666. However, the magnetic amplifier causes power loss of the diode and the saturable inductor. In recent development, the synchronous rectifier is developed to reduce the power loss of the diode, such as “Control circuit associated with saturable inductor operated as synchronous rectifier forward power converter” by Yang, U.S. Pat. No. 7,173,835. However, it requires additional devices such as saturable inductors and current-sense resistor that cause additional power consumptions.